• Step 1: In a large bowl, mix the masa harina and salt. Gradually add the warm water, kneading the dough until it forms a smooth, pliable ball. Cover and let rest for 30 minutes.
• Step 2: Divide the dough into 8 equal pieces. Roll each piece into a ball, then use your hands to flatten it into a round, thin disc, about 4 inches in diameter.
• Step 3: Place a heaping tablespoon of refried beans in the center of each disc, then top with a sprinkle of cheese and, if using, a teaspoon of minced pork. Fold the dough over the filling to create a half-moon shape, then pinch and twist the edges to seal.
• Step 4: Heat a large skillet or griddle over medium heat and brush with a thin layer of vegetable oil. Cook the papusas for 2-3 minutes per side, or until golden brown and heated through.
• Step 5: Serve the hot papusas with curtido (cabbage slaw) and salsa on the side.